Rehabilitation of brachial plexus injury in contact sport: Where are the data that underpin clinical management? A scoping review

Background Although a common injury there is a lack of published primary data to inform clinical management of sports related brachial plexus injuries. Methods A systematic search was completed in Medline, CINAHL, PubMed, SPORTDiscus and Web of Science databases and Google Scholar from inception to August 2023 according to the PRISMA-ScR guidelines. Methodological quality assessment of included articles was with the Joanna Briggs Institute tool. Studies providing primary data as to the rehabilitative management of diagnosed or suspected brachial plexus injuries sustained when playing contact sports were included. Results Sixty-five studies were identified and screened, of which, 8 case reports were included, incorporating 10 participants with a mean age of 19.8 (±4.09) years. There was wide heterogeneity in injury severity, injury reporting, physical examination and imaging approaches documented. 9 of 10 participants returned to competitive sports, though follow-up periods also varied widely. Whilst return to play criteria varied between studies, the most consistent indicator was pain-free shoulder range of motion and strength. Conclusions There is a distinct lack of data available to inform evidence-based rehabilitation management of sports related brachial plexus injury. Only 8 individual case reports contain published data reporting on 10 athletes. Further reporting is critical to inform clinical management.


Introduction
Contact sports, such as American football, rugby, or wrestling, by nature, expose participants to physical trauma and can be defined as "a sport in which participants come into bodily contact with another" [1].Tackling is an inherent part of these sports and the techniques employed typically involves contact with the opponent via the arm/shoulder, necessarily risking injury to the neck and shoulder region and, by extension, the brachial plexus.
The brachial plexus is a complex anatomical structure, comprising spinal nerves and their terminal branches in the upper extremity [2].This includes the C5,6,7,8 and T1 spinal nerves, which provide crucial sensory and motor innervation to the muscles of the upper limb to provide normal function [3].Brachial Plexus Injury (BPI) is comparatively rare in the general population, typically occurring in relation to road traffic accidents [4].In these instances of high velocity impact, the patient's injuries can be significant resulting in axonotmesis (axonal damage and Wallerian degeneration) or neurotmesis (complete transection of the nerve), require surgical exploration and intervention [5,6].
Severe BPI injuries involving axonotmesis or neurotmesis are rare in contact sports, however neuropraxia injuries (preserved axonal integrity), which are characterised by transient sensory or motor loss, are comparatively commonplace [7].Neuropraxia related BPIs are so well known that the colloquial terminology 'stinger' and 'burner' used in common sports parlance [8].
There are three primary mechanisms of injury to the brachial plexus in contact sport; direct compression of the brachial plexus at the supraclavicular region, traction injury due to depression of the ipsilateral shoulder with concomitant side flexion of the neck to the contralateral shoulder, and cervical nerve root compression due to hyperflexion or hyperextension of the neck [9,10].Any mechanism can result in any severity of injury and the sequalae of these can vary hugely, depending on the degree of nerve damage, ranging from spontaneous resolution to significant functional limitation [11].
Contact sport governing bodies have made efforts to reduce the risk of cervical spine injuries through rule changes, such as in American football, where 'spear tackling' (associated with traction injury) has been banned and players now encouraged to tackle with a 'head up' position to limit neck hyperflexion [12].Rugby administrators have also banned 'spear tackling' and are actively engaged in reducing the contact aspects of the game to mitigate serious collision-based trauma [13].Despite this, contact sport athletes remain at risk of BPI due to the inherent tackling positions and impact forces accepted during play [10].Multiple studies suggest a 'stinger' injury rate of around 2 per 10,000 athlete-exposures in American football [14,15], and cohort studies have reported that more than half of American football players suffered a BPI during their career [16,17].Similarly, Kawasaki et al. found that in a cohort of 569 rugby players, 33% reported a history of BPI, with a re-injury rate of 37% [18].Injury recovery periods were generally short but varied in this group, with 80% reporting full recovery the same day though 6% reported symptoms that lasted beyond 2-weeks.The wider impact of BPI is likely under-reported in this population due to the well know reluctance of athletes to selfreport symptoms [14,19].
The primary management of neuropraxia/stinger injuries is through non-operative rehabilitation.Effective rehabilitation management is paramount to minimise the risk of long-term complications or injury recurrence [20].Accepting a range in severity of presentation, and requirements of rehabilitation based on individual case presentation, no accepted or recognised rehabilitation management protocols exist for sports related BPI [7,[21][22][23].As such, the rehabilitative management of an individual BPI injury remains somewhat ambiguous, with return to play decisions often difficult for sports team medical staff to make [23].Athletes that report full symptom resolution are generally returned to the field at the next opportunity following this, though prolonged symptomology or recurrent injuries may trigger additional cervical imaging and wider diagnostics to inform further management [21,24].
Local rehabilitation approaches will vary and rely on; the injury presentation, the athletes reporting of symptomology, access to clinical diagnostic imaging, and on clinician experience.The quality of the underlying evidence-base which inform the various rehabilitation interventions employed is unclear, with recent reviews of stinger management noting only generic rehabilitative techniques such as 'stretching' 'strengthening' and 'electrical stimulation techniques' [7], or nebulous concepts such as postural correction and myofascial release [9], with very limited evidence referenced to support these interventions.As such, the aim of this study was to evaluate primary data underlying rehabilitative management approaches for BPI management in contact sport.

Methods
A scoping review of the literature was undertaken in line with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for scoping reviews (PRISMA-ScR) guidelines (S1 Checklist) [25].Our protocol is available via the open science framework https://osf.io/b6ptuwhich included our design framework and search strategy (documented here as supplemental data).

Information sources and search strategy
We applied the population, concept, and context (PCC) criteria to inform our search strategy that aimed to find articles that reported the rehabilitative management of brachial plexus injuries sustained while playing contact sports (S2A Table in S1 File).The search strategy was devised in conjunction with a specialist librarian and an electronic search of the following databases was conducted from inception to 21 st August 2023 in Medline, PubMed, CINAHL, SPORTDiscus and Web of Science.Boolean operators were employed in the searches as detailed in the supplemental data (S2B File in S1 File).We applied an English language restriction but no other filters to the search.Manual searches of Google Scholar and citation searching of included manuscripts were also completed.

Eligibility criteria and study selection
Due to the nature of the research question, all study types were considered for inclusion provided they were published as peer-reviewed articles and contained relevant information.We sought articles that provided primary data as to the rehabilitative management of diagnosed or suspected brachial plexus injuries sustained when playing contact sports.Contact sport was defined as a sport in which participants come into bodily contact with another [1].All grades of competitor were considered, high school, collegiate or professional level.As we were looking for the data underpinning rehabilitative management, we excluded expert opinion or narrative articles that commented on the topic without providing underpinning data to support positions, and also material that was not available as a full text publication, such as conference abstracts.
A three-part screening strategy was employed to identify relevant articles.Two investigators independently carried out the searches and screened by title.Abstracts were reviewed independently by the same two investigators and consensus reached for full text inclusion.In the event of disagreement, or doubt, manuscripts were included for full text review.Full texts were reviewed by the same two reviewers independently and final selection agreed by consensus with a third independent reviewer.

Data extraction and synthesis
We extracted data as to rehabilitation management and also relevant contextual data around the injury history, presentation, diagnosis, diagnostics and outcomes.The following characteristics of each study were extracted to a bespoke excel database: Author, year of publication, country of publication, study type, number of subjects, clinical presentation (mechanism of injury, injury history, physical examination), Additional imaging and diagnostic findings, diagnosis given, medical/surgical management, rehabilitative treatment interventions, return to play recommendations, follow-up timelines and outcomes.Data extraction forms were created, and 2 researchers independently extracted the data from included articles.The extracted data was cross-checked by a third researcher to ensure consistency.The case report nature of the information collected prohibited formal pooling of data.As such the results are presented descriptively.

Quality assessment
To assess internal validity and risk of bias, the Joanna Briggs Institute (JBI) critical appraisal tool for case reports was utilised [26].The tool comprises of an 8-point checklist addressing study design and reporting, with: Yes, No, Unclear and Not applicable selection options for each component.There are no accepted thresholds for case report study inclusion within a systematic review, [27] however, Dekkers et al. [28] emphasise that the completeness of this quality assessment tool relates to case report reliability.We report the results in this context.

Results
The literature search generated one-hundred and thirty-three articles (Medline:27; PubMed: 15; CINAHL:19; SPORTDiscus:32; Web of Science:35; Google Scholar:5) Following the removal of duplicates, 65 papers were evaluated against the eligibility criteria.After screening, only nine were eligible for full text review, with the majority of exclusions being expert opinion articles.One article was not accessible due to a broken hyperlink, and a further two were conference abstracts.Seven of these were eligible for inclusion alongside a single further article that was found through citation searching of the included publications, bringing the final number of included publications to eight.Full details are displayed in the PRISMA flowchart (Fig 1).

Follow-up, outcomes and return to play recommendations
There was no consistent approach across the included papers towards follow-up timelines, outcome reporting or return to play guidance (RTP) (Table 2).The follow-up timescales reflected assessments from 16-days to 5-years post-injury. 1 study did not state a follow-up report [30].
Objective improvements in clinical presentation were generally noted across the case studies, and nine of ten individuals returned to unrestricted participation in sport [29][30][31][32][33][34][35].RTP recommendations and the criteria for RTP clearance varied between studies.Pain-free shoulder range of motion and strength was the most commonly used indicator for the RTP decision [29][30][31].

Quality assessment
The methodological quality of the studies varied (Table 3).4/8 studies met all 9 of the evaluation criteria, [11,31,33,34] and a further 3/8 met at least 75% of items [29,30,35]. 1 study failed to reach 50% of the reporting criteria [32].Due to the limited availability of published primary research data, the decision was made to include all of these case studies in the review irrespective of reporting quality.Out with the case-report reporting quality assessment evaluation, the complexity of the brachial plexus injury characteristics and variation in management approaches resulted in poorly generalisable data.

Discussion
Despite the potential for severe and debilitating outcomes resulting from BPI in the sporting athlete, there is a distinct lack of evidence supporting rehabilitation management approaches

Kuzma et al. 2013
Nonoperative management with ice, hot packs, massage, electrical stimulation, shortwave diathermy, and over-the-counter nonsteroidal anti-inflammatory drugs (noted minimal symptom improvement).Post-operative management: Avoidance of all activity for 10-days until suture removal and wound had healed.Subsequent rehabilitation: cardiovascular activity, rotator cuff strengthening, triceps extensions, and lateral raises using resistance bands.Rapid early progression added push-ups, chin-ups, dips, seated and bent rows, and dumbbell chest presses with increasing repetitions and weight daily.
Based on clinical examination, the neurosurgeon released the patient to participate fully without restrictions in all wrestling activities.
18-days post-surgery, neurosurgical follow up.Noted negative Spurling's test, no pain, parathesis, or reproducible symptoms and normal strength.or the rationale for setting return to play criteria.Through systematic review of the published primary data for BPI rehabilitation in contact sport, only eight reports, representing ten individual case studies were found.No trials, cohort studies, or even retrospective registry-based studies are available to inform clinical management, which then, necessarily, is driven by expert opinion and the application of basic rehabilitation principles.There is a substantial difference in scale as to the management approaches required for differently presenting brachial plexus injuries.Transient 'stingers' may be isolated events that essentially self-resolve with no need for active treatment, whereas severe neural injuries can require significant medical intervention.Conservative management and rehabilitation will be the typical intervention for mild-modest neuropraxia based injury, whereas the most severe cases involving neural compromise or separation may require surgical intervention and result in disability.The 10 case reports we reflected this range of presentation.
No two studies applied the same diagnostic terminology making it hard to draw parallels across the cases.Standardisation of injury evaluation and documentation would facilitate pooling of future data to inform clinical management.Variation was also seen in clinical assessment approaches, the use of imaging/ EMG, and in the diagnostic terminology applied.Interestingly, the use of EMG was reported in a number of cases, and used to determine nerve innervation recovery and to inform return to play decisions.It is unlikely that the use of nerve conduction evaluation is reflective of 'routine' return to play management following BPI for contact sports players outside of elite sports settings, or those being treated through specialist centres.This may be the result of 'interesting cases' being reported in the literature, that may not reflect the more routine situation in clinical practice.This lack of context, and potentially quite limited generalisability, results that caution must applied as to the representativeness of the pooled findings we present for the scant literature in this area.
Despite heterogeneity in injury and in the utilised assessment diagnostics, an interesting finding of this review is differential presentation and subsequent rehabilitative management of compression and traction-based injury.Compression injuries resulted in rotator cuff weakness, whilst traction injuries were associated with biceps brachii weakness.In the acute phases of treatment, traction injuries were managed conservatively, including cold therapy, rest and/ or the contraindication of strengthening exercises, whilst athletes with compression injuries were encouraged to participate in active rehabilitation at an earlier stage.Rehabilitative management follows clinical presentation and this likely reflects clinicians treating what they find, as opposed to any specific rationale for differential management of different injury patterns, as this is not otherwise reported.We are unable to comment on the injury mechanisms leading to BPI, as details as to impact received and the setting of this are scantly reported.There are no specific notes of adverse events or reactions to rehabilitation management.Reported outcomes were generally positive and athletes returned to play following rehabilitation with no ongoing issues in 9 of 10 cases recorded.The exception being the single case involving nerve root evulsion at C5/C6, which, despite surgery, resulted in disability that impeded return to sports and substantially affected the individual's quality of life.Follow-up timeframes of the cases varied substantially though, and was often limited to a few months following injury.A narrative 'return to play' was reported, with little objective context around this statement.Rather ambiguous terminology was also used in relation to the RTP criteria applied, an example being the restoration of 'normal' cervical strength [4,29].
Whilst wider literature suggests a comparatively high prevalence of BPI in the contact sport athlete, primary data as to how to manage this injury remains unpublished or unavailable to the scientific community and practising therapists.As highlighted by multiple authors, underreporting is a concern, and whilst transient symptoms may be a factor, one must question the rigour of current sporting injury data capture and reporting.BPIs will be managed at pitchside and then in sports and community rehabilitation settings, or they will require medical escalation.From the lack of published data found, it seems no one is publishing the data and progress of these athletes following intervention.Injury reporting remains unpopular for high profile players and teams, who often rely on specific individuals to play when injured or not at their physical peak.Whilst injury data is closely guarded by sporting teams, for fear of competitive disadvantage, the lack of any published data restricts developments and improvements in sporting injury management.Specialist sports treatment centres or national sporting programmes are also likely to collect the BPI injury data that we sought in our review and the scientific community would benefit from publication of injury management and outcomes.The current situation is that rehabilitation professionals lack evidence-based diagnostic criteria, intervention guidelines, reporting guidelines, clinical outcome selection, and return to play criteria for the range of BPI presentations in collision sports.

Limitations
There are various limitations to this work.Despite wide review of four major databases and Google Scholar using pragmatic search terms and a rigorous review methodology, it is possible that relevant articles were missed.We suggest that any further such primary data as to the rehabilitation of sports related BPI is well-hidden, and not readily available to the practicing clinician.Case studies were the only sources that contained relevant data as to rehabilitation interventions for BPI.While disappointing, this is a major finding of this review.As case study data is relied on, we accept the risk that various selection and reporting biases may have influenced the cases presented and rehabilitation themes discussed.The ten case reports included in this review regarded the management of contact sports athletes, with seemingly enhanced access to diagnostic testing, assessment and treatment, it is likely these do not well represent of the wider experience of amateur athletes.Further, these may not be truly representative of the wider management of BPI in contact sport, as published case reports usually pertain to particularly interesting or challenging presentations, or those employing particular diagnostic or treatment technologies.Notably, eight of the ten cases included were reports from the United States of America and health care management may not be widely generalisable.

Conclusion
Although thought to be a relatively common injury, there is a lack of consensus guidance as to the clinical management of sports related brachial plexus injuries.The published primary data

Table 1 . Injury history, examinations and diagnosis. Author & Year Article type Participants Injury history and physical examination Diagnostic imaging Diagnostic terminology Surgical intervention
Physical Examination: Dull, burning pain in left lateral aspect of neck and left shoulder.Altered sensation in left bicep brachii, exacerbated by active and passive right cervical side-bending.Noted sharp pain in posterior cervical and left periscapular regions with active cervical extension, weakness in scapular and cervical stabilizers and C6-7 myotome.Tightness throughout the cervical spine and presumed tightness of pectoralis minor.